The surface elevation change (SEC) is a direct expression of climate changes, and closely linked to mass balance of the ice sheet. The SEC is a key essential climate variable, and is a direct measure of the imbalance between the atmospheric forcing and ice sheet dynamics. In the Greenland CCI project SEC is derived from present and past ESA radar altimetry missions, and validated by optical data (such as NASA’s IceSat).

The era of ESA altimetry missions was initiated with ERS-1 in 1992, and data from ERS-2, Envisat, CryoSat-2 and Sentinel-3 have contributed to an unbroken time series from then to present. At present there are multiple satellites in orbit (Cryosat-2 and Sentinel-3A and Sentinel-3B) contributing to the time-series; the later are ensured to be continued, with the operational approach of the EU Sentinel program.

The nature of the radar measurements enables surface penetration in the interior parts of the Greenland ice sheet and the radar measures a reflecting surface within the upper 2 meters of the snow cover, rather than the snow-air interface.

As a by-product of the work on SEC products, also a Digital Elevation Model for Greenland has been generated. 

Click here to browse and download Surface Elevation Change products

The Calving Front Location (CFL) of outlet glaciers from ice sheets is a basic parameter for ice dynamic modelling, computing mass fluxes and for mapping glacier area change. From the ice velocity at the calving front and a time sequence of Calving Front Locations the iceberg production rate can be computed which is of relevance for estimating the export of ice mass to the ocean.

The calving front location is derived by manual delineation using SAR and optical satellite data. The digitized calving front is stored as vector lines in standard GIS format. Additionally, metadata information on the sensor and processing steps are stored in the corresponding attribute table. In accordance with the URD, the vector files are provided in ESRI shape-file format.

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Products by ENVEO are also available directly from http://cryoportal.enveo.at/.

The Gravity Recovery and Climate Experiment (GRACE) twin satellites have been measuring changes in the Earth’s gravitational field between 2002 and 2017. Its follow-on mission GRACE-FO continues the time series since 2018. Time-variable gravity fields can be used to infer mass changes and mass redistributions in the Earth’s subsystems (e.g. the cryosphere). Mass variations of the Greenland Ice Sheet (GIS) can be measured with an accuracy of around 20 Gt/yr. In order to meet the IGOS (Integrated Global Observing Strategy) requirements as outlined in the GCOS-154 document systematic observation requirements for satellite-based data products for climate - 2011 Update: Supplemental details to the satellite-based component of the “Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update)”, the Greenland Ice Sheet cci (GIS_cci) produces li Mass Balance (GMB) products for the Greenland Ice Sheet from GRACE and GRACE-FO measurements. These products comprise monthly mass change time series for the entire GIS and different drainage basins as well as gridded mass change trends over different 5-year periods between.

GRACE/GRACE-FO data are available from different processing centres, including the Center for Space Research (CSR) at University of Texas, and the GeoForschungsZentrum (GFZ). Here, we use the CSR RL06 solution series (http://www2.csr.utexas.edu/grace/RL06.html), which includes spherical harmonic coefficients up to degree l_max=96.

Monthly spherical harmonic coefficients of changes in the Earth’s gravity field are available for the mission period. Different processing algorithms exist in order to derive the required information from the available data for the GIS. The round robin (RR) exercise carried out during the second phase of GIS_cci by TU Dresden has confirmed that the mass inversion and spherical harmonic filtering methods give comparable results. Therefore the GIS GMB setup is primarily based on the inversion method, method applied by DTU Space, where a direct estimate of mass changes are done in a direct least-squares generalized inverse processing. The choice of this method secures a consistency with the current Danish Polar Portal data (http://polarportal.dk), and a better and more explicit separation of Greenland mass changes from the mass changes from adjacent ice caps, especially northern Canadian ice caps in Ellesmere, Devon and Baffin Island. Details of the inversion method is outlined in the ATBD document. In addition, a second GMB product based on the regional integration approach using tailored sensitivity kernels is provided by TU Dresden.

As specified in the User Requirements Document (URD), user requirements for a gravimetric mass balance product (GMB) were found through a user survey for the Antarctic Ice Sheet cci (AIS_cci). The results were adopted for the GIS_cci. The product requirements for the GMB product are outlined below:

The drainage basins used are an aggregation of those described by Zwally et al. (2012). The figure below shows the outline of the basins. They are also employed for the GMB RR exercise.

The following movie file shows the CCI Greenland mass loss 2002-2020 from GRACE and GRACE-Follow On, both as a time series for the entire ice sheet, and monthly mass changes. Total mass loss show in Giga-Ton (GT); 362 GT of ice melt corresponds to a global sea level rise of 1 mm. The specific CCI data set is produced TU Dresden, all data available at the links provided below.

Click here to browse and download Gravimetric Mass Balance products

Products by TU Dresden are also available directly from https://data1.geo.tu-dresden.de/gis_gmb/.

The mass flow rate and ice discharge (MFID) product generated in the Greenland Ice Sheet CCI are derived from the CCI ice velocity (IV) product, the CCI surface elevation change (SEC) product (where it overlaps with the gates), and ice thickness from BedMachine (v3). Ice discharge gates are placed 10 km upstream from all marine terminating glacier termini that have baseline velocities of more than 150 m/yr. Results are summed by Zwally et al. (2012) sectors. Full details of the methods are provided in the ) the Algorithm Theorotical Basis Document (ATBD) or in Mankoff et al. (2019).

The following figure shows the sectors and gate locations within each sector.

MFID is provided as a time series CSV file where each column represents one sector from with units in Gt/yr. Additional files provide error estimates and coverage (a measure of gap-filling).

 

Click here to browse and download Mass-Flow rate Ice Discharge products.

The product is generated by GEUS.